Soybean Rust Confirmed in Indiana, But Poses No Threat

A Purdue University scientist confirmed soybean rust Oct. 17 on a leaf collected from Owen County on Oct. 15. This is the first confirmed find in Indiana this year.

This is the second year in a row that soybean rust has been confirmed in Indiana, but its late arrival means little for Hoosier farmers.

"It's too late in the season for soybean rust to have any impact on yields," says Greg Shaner, Purdue Extension plant pathologist. "We have been really fortunate that it hasn't arrived until late in the season."

The site where soybean rust was found was a late-planted field in the R6 stage of development and leaves were starting to lose their green color, Shaner says.

"Once there is a killing frost, any soybean rust in Indiana will be eliminated," he says.

Even though it's too late for the rust to do any damage, this finding is still important, explains Shaner.

"This finding documents that soybean rust arrived and most likely the infection occurred in late September or early October," he says. "It's important because there are a group of people who are modeling the long distance aerial dispersal of spores by wind and modeling the deposition of the spores as they are scrubbed out of the sky by rain."

The weather models are used to predict where the spores are going. Confirmation of soybean rust helps researchers assess the accuracy of their models and refine them.

Even though rust hasn't been a problem yet in the Hoosier state, Shaner says it still has the potential to be a problem in future years.

"This is the third year we've had the potential for rust and it's the third year we've gotten by with no problem," Shaner says. "However, I think it's premature to conclude that rust is not going to be a threat.

"The biggest uncertainty in this whole thing is that for the past three years the southeastern U.S. has been under a severe drought and rust does not do well in dry weather. When the weather pattern in the southeast returns to a more normal rainfall and higher humidity it could be a very different picture and we are not going to know until the drought breaks."